1. Field of the Invention
The present invention relates to fluid systems having a filtration device in which restriction of the filtration device can be determined by measurement of pressure. More specifically, the invention relates to devices for indicating whether a fluid filter requires replacement.
2. Description of the Related Prior Art
Fluid systems requiring filtration apparatus are an integral part of the automotive and heavy equipment industries. Engine systems, hydraulic systems and various other collateral systems require fluids such as air, oil, fuel and coolants to be at least partially contained and directed to their functional end points. For instance, in engine systems utilizing diesel fuel, extremely high-pressure pumps are utilized. These pumps have very close tolerances and may be easily damaged or disabled by particulate laden fuel. In addition, the fuel injectors of these engines are configured to deliver a spray of fuel in a specifically designed pattern. Interference with the passages, orifices or other structures of the injectors may result in a decrease in engine efficiency and/or damage to the engine itself. Most of the above-described fluid systems, including most diesel fuel systems, require at least one filter to be present.
In diesel fuel systems, a primary fuel filter is arranged between the fuel storage compartment and the high-pressure fuel pump. Fuel delivery systems for diesel engines typically include a fuel supply pump for delivery of partially pressurized fuel to the high-pressure pump. These fuel supply pumps can be arranged in the fuel storage compartment or close to the high-pressure pump. When arranged in the fuel storage compartment, the supply pump pressurizes the fuel supply line leading to the high-pressure pump. When arranged close to or as part of the high-pressure pump, the supply pump creates negative pressure in the supply line between the fuel storage compartment and the supply pump.
Depending on such things as preventative maintenance scheduling, fluid quality, operating conditions and the like, filters become restricted or clogged at various rates. Filter occlusion may adversely impact system efficiency and in some cases may damage or destroy system components. In other cases restriction of the filter can result in filter failure which may allow highly contaminated fluid to reach portions of a high pressure pump or fuel injection system, resulting in extremely high repair costs for those devices.